Process for Incorporating a Dry Treatment Product Into a Liquid Waste

ABSTRACT

A process for treating and disposing a liquid waste, which is solidified prior to disposal, includes steps of adding to said liquid waste a dry treatment product generally comprising approximately 25% to 75% bentonite clay and respectively 75% to 25% of a liquid-sorbing polymer, subjecting the liquid waste to a single pass high shear mix so as to incorporate the treatment product into the liquid waste with increased dispersion and reduced agglomeration, subjecting the treated liquid waste to a retention time suitable for solidification, and disposing of the solidified liquid waste. The liquid waste preferably is recirculated prior to addition of dry treatment product so as to permit a calibration of the characteristics of the liquid waste, and subsequent determination of the correct rate of dry treatment addition.

This application is a division of copending application Ser. No.11/994384 filed Dec. 31, 2007 as the U.S. national stage ofinternational application PCT/CA2006/01099, filed Jul. 5, 2006, whichclaims benefit of U.S. provisional application 60/695887, filed Jul. 5,2005.

FIELD OF THE INVENTION

The present invention relates to a method for treating liquid wastematerial. In particular, the present invention relates to a flow-throughmixing process for incorporating a dry treatment product into a wastestream

BACKGROUND OF THE INVENTION

A wide variety of industries produce liquid waste and consequently, arein a constant search for economical means for disposal. While disposalto local waste treatment/disposal facilities is one option available,the costs associated with this means are often excessive.

Solid waste disposal is a less expensive means of waste disposal. Assuch, conversion of liquid waste into a “dry” or “solid” form isdesirable, but not easily attained. A variety of treatment products havebeen used including sawdust, lime/Portland cement, zeolites and clays.Unfortunately, these products generally result in excessive bulk up,resulting in considerable transportation costs. For example, it is notuncommon with the prior art technologies to experience a bulk-up ofanywhere from 40%-300%. A further issue with prior art technologies isthat leaching of the liquid waste from the treated product can occur,thus presenting further environmental issues during both transport andsolids disposal.

In many instances, the excessive bulk-up experienced, and the poorretention of the liquid waste by the treatment product is due to a poorincorporation of the treatment product into the waste stream. In manyinstances, the waste is generated at locations where transportation ofliquid waste off-site is very difficult. For example, in drillingoperations, treatment of the resulting liquid waste, that is the liquidcontaining the drilling slurry as well as any contaminants (i.e. debris,hydrocarbons, etc.) requires a step-wise approach that is spread over alengthy period of time. For example, in regions difficult to access(i.e. northern areas), equipment is first transported to a drilling siteduring winter months and drilling operations commence. The followingsummer, the resulting liquid waste that was accumulated during thewinter drilling season is batch treated with prior art technologies(i.e. sawdust). If removal from the site is necessary, (i.e. withhydrocarbon contaminated waste), the treated liquid waste is transportedout of the site the following winter. This treatment regimen is lengthy,very expensive and subject to environmental scrutiny.

There is clearly a need for an improved treatment process that is ableto effectively and efficiently process liquid waste into a “dry” or“solid” product that is suitable for solids disposal. There is further aclear requirement for an apparatus and process that permits theefficient incorporation of a dry treatment product into a waste stream,so as to reduce the bulk-up experienced with prior art technologies.

SUMMARY OF THE INVENTION

Broadly stated, the present invention provides an apparatus and processfor converting liquid waste material originating from a variety ofindustries (i.e. horizontal directional drilling, oil drillingoperations, etc.) into solid waste allowing for disposal as a solidproduct, thereby reducing disposal costs and potential environmentalissues related to transport and disposal of liquid waste.

According to an aspect, there is provided a single-pass flow-throughmixing apparatus for incorporating a dry treatment product into a wastestream, said apparatus comprising:

-   -   a pump for directing a liquid waste from a storage pit/tank;    -   a mixer receiving said liquid waste from said pump, said mixer        comprising a jet nozzle, a venturi tube and a high-shear        assembly;    -   a valve downstream of said mixer for either recirculating said        liquid waste back to said storage pit/tank via a recirculation        conduit, or directing said liquid waste to a discharge conduit;    -   wherein said recirculation conduit defines a calibration loop        for determining the appropriate treatment regimens based on the        characteristics of the waste liquid;    -   said recirculation conduit also permitting homogenization of        said pit/tank contents prior to addition of said dry treatment        product; and    -   wherein dry treatment product introduced at the mixer is        subjected to high shear forces, thereby incorporating the dry        treatment product into the waste stream with increased        dispersion and reduced agglomeration.

According to another aspect, there is provided a process for treatingand disposing of a liquid waste wherein said liquid waste is solidifiedprior to waste disposal, said process comprising:

-   -   adding to said liquid waste a dry treatment product generally        comprising approximately 25% to 75% bentonite clay and        respectively 75% to 25% of a liquid-sorbing polymer,    -   subjecting said liquid waste to a single pass high shear mix so        as to incorporate said treatment product into said liquid waste        with increased dispersion and reduced agglomeration;    -   subjecting the treated liquid waste to a retention time suitable        for solidification; and    -   disposing of the solidified liquid waste.

According to a further aspect, there is provided a process forsolidifying a liquid waste prior to waste disposal, said processcomprising:

-   -   adding to said liquid waste a treatment product generally        comprising bentonite clay and a liquid-sorbing polymer,        subjecting said liquid waste to high shear forces so as to        incorporate said treatment product into said liquid waste with        increased dispersion and reduced agglomeration; subjecting the        treated liquid waste to a retention time suitable for        solidification;    -   storing said treated liquid waste to allow for evaporation of        water, thereby resulting in a decrease in overall volume        relative to a predetermined initial volume of liquid waste to be        treated.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram of an apparatus for treating liquid wastematerial according to one embodiment.

FIG. 2 is a schematic diagram of an apparatus for treating liquid wastematerial according to an alternate embodiment, in which the apparatus isautomated.

FIG. 3 is a perspective view of a prefilter suitable for use with theapparatus shown in either of FIG. 1 or 2.

FIG. 3 a is a schematic diagram of a plurality of prefilters as shown inFIG. 3, the prefilters being shown in parallel.

FIG. 4 is a schematic diagram of a mechanical mixing chamber suitablefor use with the apparatus shown in either of FIG. 1 or 2.

DESCRIPTION OF THE EMBODIMENTS

In the following description, embodiments of an apparatus and processfor treating liquid waste material are described. In general, theprocess includes the treatment of liquid waste, for example liquid wasteoriginating from horizontal directional drilling (HDD) or oil drillingoperations wherein this waste is “solidified” by way of chemicaltreatment. More specifically, the process includes 4 basicoperations: 1) liquid waste material delivery, 2) chemical/physicaltreatment to promote sorption of liquid and conversion of the liquidwaste into a solid form, 3) “solidification” or set-up (i.e.gelification) of the liquid waste with optional mechanical kneading, and4) final disposal. The final solidified product can then be disposed ofvia known options available for solid wastes.

The present invention provides an effective real-time liquid wastematerial treatment process that is operated in a continuous, single-passflow-through mode, as opposed to batch operation. Considering thevariable nature of liquid waste material, the treatment process ishighly adjustable to accommodate the specific characteristics of theliquid waste material being treated. The process is operated eithermanually, or automated by way of computer control. The treatmentapparatus is sufficiently compact to allow mounting on a trailer. Thisallows the apparatus to be used on-site, close to the source, thusreducing the need for costly transport, as well as reducing the inherenthazards and regulatory approvals associated with waste transport.

Turning now to FIG. 1, an apparatus for treating liquid waste materialis shown and generally identified by reference numeral 10. Liquid wastematerial is generally collected in a pit or tank 12, and may contain avariety of contaminants such as hydrocarbons originating from oildrilling operations. While this waste material is generally referred toas liquid, it contains a varying degree of solid matter including soil,rocks and other debris generated during drilling operations. Inoperation, the liquid waste is drawn up through inlet conduit 14 fromthe pit or tank 12 through a size regulated inlet 16 by the trash pump18. The liquid waste is directed through coarse filter 20 which reducesthe amount of debris capable of plugging constricted areas of theoverall apparatus. The coarse filter 20 also serves to homogenize thefluid stream so as to improve the overall treatment process.

After exiting trash pump 18, the liquid waste travels via a conduit 22to a mixing zone 24. In line with conduit 22 is a flow meter 26 thatprovides the operator with a measure of liquid waste flow through thesystem. As shown, a minor portion of the liquid waste is directed awayfrom conduit 22, through conduit 28 to a generally conical swirl bowl30. This diverted stream is used to facilitate the addition of drytreatment product in swirl bowl 30, as described below. The liquid wastepassing through conduit 28 is directed through a second filter 32 so asto reduce the likelihood of blockage in constricted areas of the swirlbowl. To control liquid flow through conduit 28, an on/off valve 34 andmetering valve/orifice 36 are also provided.

The dry treatment product used to treat (i.e. chemically solidify orgel) the liquid waste is metered into the swirl bowl 30 with a meteringbulk hopper 38. As the dry treatment product falls into the swirlchamber 30, it is combined with the fluid delivered via conduit 28, andflows down into the mixing zone 24. To facilitate this delivery, thefluid delivered via conduit 28 is introduced at the top of the swirlchamber 30 at an angle that causes the fluid stream to adopt a swirlingmotion as it follows the cone shape towards the mixing zone 24. In thisway, even small amounts of dry treatment product are efficientlydelivered to the mixing zone 24. In mixing zone 24, the product fromswirl bowl 30 and the liquid waste delivered via conduit 22 arecombined, this process being facilitated by placement of nozzle 40 andventuri tube 42, and the subsequent shear assembly 44. The nozzle 40,venturi tube 42 and shear assembly 44 facilitate mixing by providing ahigh shear mix to the combined product. The effect of the high shearmixing is to increase the surface area contact between the dry treatmentproduct and the liquid waste, so as to reduce agglomeration and increasedispersion, thereby increasing efficient usage of the dry treatmentproduct. With regard to the nozzle 40 and venturi tube 42, in apreferred arrangement, the dimensions for these structures is generallyin the region of 11/16 inch I.D. and 1 inch I.D., respectively.Downstream of mixing zone 24, the treated liquid waste is directedthrough discharge conduit 46 into a suitable retention basin 48,suitable for subjecting the treated liquid waste to a residence timenecessary for solidification of the waste material. A suitable retentionbasin 48 can take on any number of forms, such as a pit or container ofa dump truck.

The apparatus described above and shown in FIG. 1 is switchable betweena discharge mode and a recirculation mode in which the liquid waste isdirected back into the pit or tank. Recirculation of the liquid waste isuseful during start-up (i.e. pump priming), calibration of the system,cleanup or maintenance operations, as well as shut-down. Recirculationis generally performed with untreated liquid waste so as to avoid theaddition of dry treatment product to the pit or tank 12. In manyinstances, the apparatus is operated in recirculation mode prior to drytreatment product delivery so as to homogenize the liquid contents inthe pit or tank 12, thus ensuring a more consistent treatment regimen.This pre-run recirculation also permits the calibration of the apparatusso as to enable either the operator (in manual mode) or the centralprocessor (in automatic mode; described below) to determine the correctamount of dry treatment product necessary to treat the particular liquidwaste. This has the advantage of reducing the amount of wastage of thedry treatment product, thereby reducing overall cost. Furthermore, sincethe apparatus is operated as a single-pass, flow-through apparatus, thispre-run calibration step reduces the likelihood that the dischargedtreated product is insufficiently treated which could lead to inadequatesolidification and possibly leakage of contaminants. To enable operationin recirculation mode, conduit 46 is fitted with a 2-way valve 50 thatis capable of diverting the liquid waste back to the pit or tank viarecirculation conduit 52.

The apparatus described above is suitable for use in manual mode. Bycontrolling pump 18, valves 34, 36 and 50, as well as metering hopper 38and swirl bowl valve 39, an operator is able to tailor the treatmentregimen for a particular application. As required, the apparatus can befitted with flow meters (i.e. flow meter 26) to obtain information abouta particular run, enabling the operator to make adjustments asnecessary.

In an alternate embodiment, the apparatus is set for automatedoperation, as shown in FIG. 2. To automate the apparatus, a number ofmonitoring/control devices are added into the apparatus, as well as acentral processor (not shown). The automation of the treatment regimenis dependent in part upon the characteristics of the liquid waste. Toobtain these characteristics in “real-time”, the apparatus is providedwith a fluid flow meter 70 and a metering scale 72 in conduit 22.Metering scale 72 serves to calculate the weight of the “mud”, that isthe weight of the solids content in the liquid waste stream on a massper unit volume basis (i.e. lbs/gal). In operation, the optimal flow ofliquid waste through the apparatus is approximately 80 gallons perminute. As such, based on this flow rate, and an estimated weight of“mud” calculated by way of metering scale 72, the metering bulk hopper38 is able to deliver the appropriate amount of dry treatment product.In general, for solidifying a liquid waste, the amount of product to beadded to the liquid waste ranges from 1 to 10% (wt/wt) based on a weightpercentage, but is preferably in the range of 2 to 6% (wt/wt), and morepreferably approximately 3% (wt/wt). The data being received from thefluid flow meter 70 and the metering scale 72 is fed into a centralprocessor (not shown) which optimizes dry treatment product delivery byway of metering bulk hopper 38. This “real-time” monitoring of theliquid waste provides a greater degree of accuracy with respect todispensing the dry treatment product. In addition, the central processoris able to control flow rates by controlling pump 18, as well as thevarious control valves in the apparatus (i.e. valves 34, 36, 50).Automation of the process also allows for auto shut-off in the eventthat the treatment powder bridges or runs out, thus reducing thelikelihood that untreated liquid waste continues through the apparatus.

In the embodiment shown in FIG. 2, also provided is a fresh water inlet84 in conduit 21. The fresh water inlet 84 provides a way to flush theapparatus during a cleaning session. Fresh water inlet 84 alsofacilitates dilution of the liquid waste should dilution be necessaryfor a particular application. To reduce the likelihood of backflow offresh water towards the pit, conduit 21 is fitted with a check valve 86.Control of the inflow of fresh water is provided by way of valve 88which may be operated manually, or through control from a centralprocessor. The supply of fresh water can be provided by either asuitable tank or basin, or by way of a direct supply line, depending onthe availability of a fresh water source.

For certain liquid wastes, it will be appreciated that a pre-filtrationstep will be necessary to remove large debris. Shown in FIG. 3 is anoptional prefilter 54 for fitting into inlet conduit 14. The prefilter54 includes a holding container 56 having a lower funnel region 58 and abottom valve assembly 64. As the liquid waste gets pumped into theprefilter 54, the larger debris (i.e. rocks) that cannot pass throughholes 62 fall to the bottom of the holding container 56. The liquid inthe prefilter, together with any of the smaller debris being carried bythe liquid waste stream passes through holes 62 and continues onwards topump 18 and the rest of the apparatus. To remove the larger debris inthe holding container 56, the bottom valve assembly 64 is opened,allowing the collected debris to fall from the container for disposal.While a variety of valve assemblies (i.e. knife valves) are suited forthe above noted application, it will be appreciated that the prefilter54 can include a hinged or removable cap to allow removal of collecteddebris from holding container 56. To facilitate insertion of theprefilter 54 into inlet conduit 14, the prefilter 54 and inlet conduit14 can be provided with quick release connectors 66. In addition, whilethe above description has been limited to a single prefilter assembledin-line with inlet conduit 14, it is also possible to assemble multipleprefilters in parallel as shown in FIG. 3 a.

In automated applications using multiple prefilters, the centralprocessor is operable to control flow through the prefilters arranged inparallel by controlling valves 76, 78, 80 and 82. For example, duringoperation, it may be advantageous to open valves 76 and 78, whilekeeping valves 80 and 82 closed, thereby directing the waste streamthrough prefilter 54 a. When the central processor detects thatprefilter 54 a is full (i.e. by weight, back pressure, etc.), valves 80and 82 are opened while valves 76 and 78 are closed, thereby directingthe waste stream through prefilter 54 b. During this time, prefilter 54a can be cleaned out by way of bottom valve assembly 64, so thatcontinual operation by switching back and forth between the twoprefilters is possible. In automated mode, bottom valve assembly 64 canbe opened and closed by way of a switch that is controlled by thecentral processor. It is clear from the above discussion that theability to monitor the process and adapt for changes allows continualrunning of the apparatus and process, without need to stop every timethe liquid waste changes in viscosity or consistency.

It will be appreciated that the coarse filter 20 and shear assembly 44are subject to accumulation of larger debris. In a preferredarrangement, these filters have holes that are about ¼ inch I.D. Assuch, these devices may be mounted using quick-couplers for cleaningpurposes; the filter housings may include at least one access opening topermit manual flushing. Similar to the pre-filters described above, itwill also be appreciated that fixtures such as these that are subject toaccumulation of larger debris may be implemented in multiples positionedin parallel. This way, in the event of a blockage, an alternate unit isavailable for use. Switching between the multiple units placed inparallel can be either manual, or automated in a similar manner asdescribed above for the pre-filter assemblies.

It will be appreciated that additional trash pumps can be incorporatedinto the apparatus 10. In instances where the distance from the pit/tankto the unit is considerable, an additional pump 94 can be incorporatedinto inlet conduit 14, as shown in the embodiment of FIG. 2. In suchcases, the system is includes a return loop 96 facilitated by 2-wayvalve 98. The system can also include an additional trash pump 100 onthe discharge conduit 46 in the event that the retention basin ordisposal location is of considerable distance from the treatment unit.It will also be appreciated that alternate pumps/pump arrangements canbe implemented as would be determinable by one skilled in the art. Forexample, the pumps can be engine driven, hydraulically driven,submersible, centrifugal or above ground.

As presented above, following mixing of the dry treatment product intothe liquid waste, the mixture “solidifies”, gels or sets in thereceiving retention basin or disposal location. For applications wheremechanical agitation is required during the residence time, a mechanicalmixing chamber can be incorporated into the system. A suitablemechanical mixing chamber can include a liquid mixing auger to handlemore fluid waste, a kneading auger to handle more solid waste, or acombination of both. An example of a mechanical agitation system thatcan be added onto the discharge end of the apparatus is shown in FIG. 4.In this combined system, the treated liquid waste moves through thefirst liquid auger 90, the treated liquid waste gradually becoming moresolid, passing in turn to the second kneading auger 92, subsequent towhich the end product is discharged for disposal.

The apparatus described above can be assembled on a transportableplatform (i.e. a truck bed) so as to allow portability and facilitateeasy transport on-site, where needed. The present invention offersversatility in that it can be automated to adjust to changingconditions, for example changes in consistency and viscosity of theliquid waste. As such, the technology can be applied to a wide range ofliquid wastes, for example wastes originating from HDD operations, oildrilling operations and other industrial processes. The process may alsofind application in treating industrial and biological wastes.

The dry treatment product suitable for use with the above describedapparatus and process generally comprises at least one bentonite clay(i.e. sodium bentonite or calcium bentonite) and at least onedry/powdered liquid-sorbing polymer (i.e. anionic or cationic waterabsorbent polymers, non-aqueous absorbing/adsorbing polymers, etc.). Ingeneral, the dry/powdered liquid-sorbing polymer serves to “dry” theproduct, while the bentonite clay component effectively encapsulates anychemical entities in the waste stream, thereby reducing the likelihoodof leaching of liquid waste from the end product. The use of the abovedescribed apparatus enables highly efficient single-pass mixing of thedry treatment product into the liquid waste stream. The apparatus canthus be operated in flow-through mode so as to simplify operations andreduce overall cost. As indicated in the background above, prior arttechnologies have used less effective treatment products with standardmixing regimes, resulting in a far less efficient incorporation of drytreatment product. The above described apparatus is able to take fulladvantage of the physicochemical nature of the dry treatment product bysubjecting the combined liquid waste/dry treatment product to shearforces that ensure increased surface area contact between them. Theapparatus is operable to reduce agglomeration and increase dispersion ofthe dry treatment product upon contact with the liquid waste, therebyreducing the formation of clumps and therein unused dry treatmentproduct. For dry treatment product comprised of bentonite clay andliquid-sorbing polymer, the ratio of bentonite clay to liquid-sorbingpolymer will vary depending on the application. In general, with wastescontaining a higher proportion of hydrocarbons, a higher bentonite claycontent is desirable. For example, with HDD operations where thehydrocarbon content is quite low, the blend is generally 25% bentoniteclay to 75% polymer. For oil field or other industrial wasteapplications, the ratio may be upwards of 75% bentonite clay to 25%polymer. It may also in certain applications be particularlyadvantageous to use a variety of different bentonite clays to obtain thedesired sorption and encapsulation qualities.

A treatment regimen using the above apparatus and dry treatment productresults in a “solidified” treated product that is reduced in volumecompared to the initial volume being treated. For a given volume beingtreated, once the dry treatment product is added (i.e. 4% wt/wt), theresulting solidified product after 48-72 hours demonstrates a reductionin overall volume of up to 20%. This reduction appears to be related tothe evaporation of liquid from the “solidified” waste, resulting in adecreased overall volume. Compared to conventional bulk-up technologiesthat exhibit anywhere from 40-300% increase in volume, the reduction involume observed provides a significant savings with respect to solidwaste disposal. Furthermore, the encapsulation of the contaminants (i.e.salts) in the “solidified” waste appears to be very effective as theextractability of these contaminants is reduced. While not completelyunderstood, it is believed that the high surface area contact betweenthe dry treatment powder and the liquid waste provided by theaforementioned apparatus ensures a high degree of encapsulation of thecontaminants, thereby reducing the extractability of these compounds.

The ability of the bentonite clay/polymer blend to “dry” or “solidify”the liquid waste with little or no leachate offers the possibility ofdisposing the waste material on site, as permitted by environmentalregulations. This would dramatically decrease the overall cost ofdisposal, as transport from the site would not be necessary.

It will be appreciated that although the aforementioned apparatus hasbeen described with respect to bentonite clays and liquid-sorbingpolymers as the solidifying/drying agent, the apparatus can beeffectively used with a wide range of other dry treatment productssuited for solidification, gelification or drying of liquid wastes. Thehigh surface contact between the dry treatment product and the liquidwaste achieved by the present apparatus makes the unit especially suitedfor situations where a highly efficient incorporation of dry product isrequired in a liquid stream.

Having regard to the effective mixing offered by the aforementionedapparatus, it will also be appreciated that the apparatus may be used asa mixer for incorporating other dry treatment products (i.e.non-solidifying treatment products) into liquid wastes. In thiscapacity, dry treatment products may be effectively added with highlyeffective homogenization at amounts as low as 0.01% (wt/wt).

The aforementioned apparatus permits a single pass highly efficientdispersion of a dry reagent in a liquid waste stream using multiplepoints of shear, wherein used with combinations of dry reagents andwaste stream that exhibit rapid or short term gel, set, orsolidification, results in a novel waste liquid solidification processof particular value where combinations result in a reduction in overallwaste volume.

It will be appreciated that, although embodiments of the invention havebeen described and illustrated in detail, various modifications andchanges may be made. While preferred embodiments are described above,some of the features described above can be replaced or even omitted. Asmentioned, additional pumps may be used depending on the distances overwhich the liquid waste is required to pass. While 80 gal/min isconsidered an optimal flow for the apparatus, the operational range is70 to 120 gal/min, with higher or lower flow rates also possible withalternate pumps readily available on the market. A number of filters areshown incorporated into the system. Depending on the application, it maybe possible to remove, for example, the coarse filter when the liquidwaste is sufficiently fluid and low in large debris. In someapplications, it may not be necessary to add fluid to the swirl bowl.For certain liquid waste, it may be necessary to supplement the liquidwaste with additives (i.e. soap additives for separation/break-up ofoils in the liquid waste). In such instances, the course filter servesto mix the additives into the waste stream prior to addition of the drytreatment product. Still further alternatives and modifications mayoccur to those skilled in the art. All such alternatives andmodifications are believed to be within the scope of the invention.

1. A process for treating and disposing a liquid waste wherein saidliquid waste is solidified prior to waste disposal, said processcomprising: adding to said liquid waste a dry treatment productgenerally comprising approximately 25% to 75% bentonite clay andrespectively 75% to 25% of a liquid-sorbing polymer, subjecting saidliquid waste to a single pass high shear mix so as to incorporate saidtreatment product into said liquid waste with increased dispersion andreduced agglomeration; subjecting the treated liquid waste to aretention time suitable for solidification; disposing of the solidifiedliquid waste.
 2. The process of claim 1, wherein said liquid waste isrecirculated prior to addition of dry treatment product so as to permita calibration of the characteristics of the liquid waste, and subsequentdetermination of the correct rate of dry treatment addition.
 3. Theprocess of claim 1, wherein said liquid waste is prefiltered prior toaddition of dry treatment product.
 4. The process of claim 1, whereinsaid liquid-sorbing polymer is a water-sorbent polymer.